DE 20 2009 017 016 U1 discloses a crash box injection molded out of a fiber-reinforced plastic, in which two hollow bodies stacked one inside the other and connecting elements extending between the hollow bodies form supporting walls, which extend in the loading direction of the crash box, between a bumper-side end face and a body-side end face of the crash box. The end faces themselves are open. Collision energy is absorbed by a deformation of the supporting walls. A supporting wall that runs exactly in the loading direction has a high deformation resistance while it remains undeformed. However, this resistance collapses quickly just as soon as the supporting wall begins to give way laterally under pressure.
For achieving a uniform energy absorption over the entire compressible length of the crash box, a stepped structure of the supporting walls of the inner hollow body is provided, in which each step can collapse separately and thereby absorb energy. However, the amount of energy that can be dissipated in this way is limited for several reasons. On the one hand, the amount of energy that can be absorbed by an individual step depends on its wall thickness, but the larger the wall thickness, the greater the distance between the steps must also be, so that they can collapse separately from each other, and the fewer steps can be accommodated in a crash box with prescribed dimensions. On the other hand, in the event of a collision, both hollow bodies ultimately are supported by way of a flange at the tip of the side member—which usually is designed as a hollow profile—on its longitudinal walls. Only one of the two hollow bodies can extend in the elongation of the longitudinal walls of the side member, and the one that does not do so cannot be so stiff as to deform the flange in the event of a collision.
Accordingly, there is a need in the art to provide a crash box that exhibits a high-energy absorption capacity in relation to its weight.